Travelling cranes for lifting and lowering loads are generally known. Such travelling cranes are characterised by one or two beams which at their ends are displaceable on rails via travelling mechanisms. These rails are disposed in warehouses on their longitudinal sides in the region of the roofs, for example. A crane trolley, on which a hoisting winch is mounted, is displaceable on or at the longitudinal beam in a transverse manner with respect to the travel direction of the longitudinal beam. Such hoisting winches consist substantially of a cable drum which is driven in a lifting and lowering direction by means of a gearbox and an electric motor. In order to be able to lift large bearing loads of e.g. 80 t or 150 t by means of a hoisting winch such as this, the cable is typically reeved. The reasons for this are predominantly financial, since reeving is more cost-effective than corresponding dimensioning of the gearbox which is a function of cable strength and drum diameter. Typically, an 8/2 reeving is used, such as for an 80 t hoisting winch, or a 12/2 reeving is used for a 150 t hoisting winch. Such reevings ensure that the load hook is formed as a lower block and in the region of the hoisting winch upper blocks are provided in the form of pivotably suspended pulleys. An 8/2 reeving requires the use of a double-grooved cable drum having cable grooves running in opposite directions, from which the two ends of a cable run out and are guided by a total of three upper blocks and four pulleys in the region of the lower block. Since in the region of the lower block a total of 8 cable strands are fed in and out and two cable strands are wound or unwound by the cable drum, this is referred to as an 8/2 reeving. Use of two driven cable strands of a cable drum, which run out from cable grooves running in opposite directions, has the advantage that during the lifting and lowering procedure the lower block moves only in the lifting and lowering direction and does not travel along the axis of rotation of the cable drum. However, the above-described large reevings of 8/2 or 12/2 also require correspondingly longer cable lengths. As a consequence, a correspondingly long cable drum must be provided or the diameter thereof must be selected to be larger. However, the length of the cable drum is limited by the maximum permissible deflection angle transverse to the longitudinal direction of the cable drum. In general, the cable drum diameter is thus increased. A larger cable drum diameter requires a larger gearbox output torque. A maximum gearbox output torque of a gearbox can thus limit the maximum possible bearing load of the hoisting winch. In the case of large cable deflection angles the cable is also subjected to a substantial stress loading. This leads to a reduction in the serviceable life of the cable and also in the serviceable life of the cable drum and all deflection rollers. This also makes it more difficult to theoretically calculate the serviceable life of the cable using the existing cable deflection angle which changes in the longitudinal direction of the cable drum.
Furthermore, German patent DE 101 17 466 B4 discloses an electrical hoisting winch for use as a stage winch. Such stage winches are used for lifting and lowering curtains and scenery items. Typically, the curtains or scenery items are suspended via several cables at several points along the width of a stage. In order to ensure that the curtains and scenery items are lifted and lowered in a uniform manner, the cables must be wound or unwound synchronously by the hoisting winch. Such hoisting winches thus comprise hoisting winches which are disposed next to each other and are mounted on a common drum shaft. In this case, the drum shaft is driven by one or several electrical drive motors via a gearbox. Since in the case of a stage several curtains and pieces of scenery are disposed at a small spaced interval one behind the other as seen in relation to the depth of the stage, it is not possible for several hoisting winches to be disposed one behind the other, as their installation width is too large. Rather, the hoisting winches for this purpose have at least one deflection roller for each cable, in order to deflect the cable, which in each case runs out horizontally from the cable drum, to a vertical direction in the direction of the stage. These deflection rollers are disposed in a positionally fixed manner on a crossbar which is supported on the hoisting winch. In the case of this hoisting winch, in order to ensure that the curtains and scenery items are lifted and lowered in an absolutely uniform manner, provision is additionally made to avoid any lengthening and shortening of the cable length between the cable run-out points of the cables from the respective cable drum and the deflection roller, which would occur on account of the cable run-out point travelling along the cable drum. For this purpose, the entire hoisting winch is disposed on a drum slide which is displaceable in the longitudinal direction of the drum axis in relation to a stationary support frame of the hoisting winch. The drum slide is displaced relative to the support frame and the deflection rollers by means of a spindle drive such that the drum slide is displaced synchronously with the rotation of the drum by a displacement distance of about one cable diameter per drum rotation. This ensures that the respective cable running out from the cable drum runs into the deflection roller approximately at a right angle to the axis of rotation of the deflection roller. The cable length between the cable run-out point of the cable drum and the deflection roller is therefore not lengthened or shortened, as a result of which there is also no fluctuation in the lifting and lowering speed which this otherwise causes.
Moreover, Japanese laid-open document JP 2001-2379 A discloses a travelling crane having a travelling trolley which is displaceable on a longitudinal beam of the travelling crane via rollers. The travelling trolley typically has a hoisting winch having a cable drum. The hoisting winch and therefore its cable drum are displaceable relative to the travelling trolley via further rollers. In this case, the travel direction of the travelling trolley and the longitudinal direction of the cable drum correspond. The cable drum is displaced relative to the travelling trolley by means of a hydraulic cylinder. This additional displaceability of the cable drum relative to the travelling trolley is intended to ensure that the cable run-out point of the cable remains in one location in relation to the longitudinal extension of the cable drum during winding and unwinding of the cable.
U.S. Pat. No. 5,423,438 discloses a travelling crane having a travelling trolley which comprises two hoisting winches each with a cable drum. The cable drums are disposed in parallel and spaced apart from each other and can be rotated in opposite directions. A first and second common cable can be wound and unwound from the cable drums. The two cables are reeved via a first or second cable pulley of a lower block and run out with a total of four cable strands from the cable drums. The cable pulleys are rotatably mounted in the lower block via spindles extending in parallel with the axes of rotation of the cable drums and are freely moveable and displaceable along same. The cable run-out points which travel away from each other or towards each other along the cable drums during winding and unwinding of the cables produce variable cable run-out angles between the individual cable strands and the cable drums or cable pulleys. By virtue of the cables which run out, axially effective forces are introduced into the cable pulleys which consequently are tracked automatically to the travelling cable run-out points. As a consequence, the cable run-out angles are reduced.
German laid-open document DE 1 192 381 B describes a travelling crane having a travelling trolley which comprises four hoisting winches each comprising a cable drum. Each of the cable drums serves to wind and unwind a cable which at its free end is attached to a load receiving means via a hook. The cables running out from the cable drums are each guided via a deflection roller. In order to ensure that the cables encounter the deflection roller at a constant cable run-out angle, the travel of the cable run-out points of the cables along the cable drums is equalised by displacing the cable drums along the rotational spindles, which support them, by means of the cable forces which act accordingly upon the cable drums.
European patent application EP 0 571 207 A1 relates to a cable guiding device for winding and unwinding a cable in multiple layers onto a cable drum of a hoisting winch. The cable drum is attached to a slide. In order to ensure that the cable run-out point remains constant in the region of the guide rollers for the purpose of winding the cable in an orderly fashion, the slide is displaceable along two rails via rollers relative to a positionally fixed arrangement of guide rollers. The displacement of the slide is likewise effected by the occurring cable forces.
British patent application GB 714 071 A discloses a dockside crane having a telescopic jib and a telescopic mast suspended thereon. In the interior of the jib, a hoisting winch is horizontally displaceable via a travelling trolley, whose cable is guided through the interior of the jib or the mast. In order to ensure that the cable, which runs out vertically downwards from the cable drum of the hoisting winch, maintains the central position in relation to the mast during winding and unwinding in spite of the cable run-out point which travels in relation to the cable drum, the travel of the cable run-out point or of the cable is counteracted by corresponding displacement of the travelling trolley along the jib.